Driving device

ABSTRACT

A driving device comprises a source of hydraulic fluid under pressure, a working arrangement (6) having a working chamber (7) intended for receiving hydraulic fluid and a working member (8) adapted to be put in motion on respective fluid supply to and fluid evacuation from the working chamber. Conduits (20, 29, 30) are provided for respective supply to and evacuation from the working chamber (7) of hydraulic fluid. A valve (16) is adapted to, in a first state, direct fluid to the working chamber and, in a second state, allow evacuation of fluid from the working chamber. An apparatus (17) are provided for returning the working member to a starting position. These apparatus comprise an ejector arrangement adapted to generate a negative pressure evacuating the working chamber as a consequence of flow of fluid through the ejector arrangement. The hydraulic fluid source is constituted by a high pressure washing unit known per se or of an arbitrary nature.

This application is a Rule 371 of PCT/SE94/00041, filed on Jan. 21,1994.

FIELD OF THE INVENTION AND PRIOR ART

This invention is related to a driving device according to theprecharacterizing parts of the appending FIGS. 1-3. The driving deviceaccording to the invention may be used in any conceivable connectionswhere it is desired to put a working member in motion. Although it canbe mentioned as an example that the working arrangement could form apart of machines for splitting wood pieces, more specifically so calledfire wood cleaving machines, it can be mentioned as other examples onapplications general use as jacks, presses, bending apparatus etc, theworking member of course being provided with an arbitrary tool forcarrying out the function aimed at.

Fire wood cleaving machines of the kind mentioned in the introductionare known per se. By way of example, reference can be made to WO 92/11980 (PCT/SE 91/00914), the European patent publication No. 0 051 853,the Swedish publication for inspection No. 7904914-4 (416 903) and theSwedish publication for inspection No. 8304029-5 (453 898).

The two first mentioned publications are particularly interesting in thepresent connection. The devices more closely described therein sufferfrom several important disadvantages. One of these disadvantages residesin the need for springs for returning the working member to a startingposition, these springs having to be tensioned during the workingstroke. Such springs tend to become fatigued with time, which requiresexchange of springs. Furthermore, power for tensioning the springs isrequired during the working stroke, which increases the total powerrequirement of the working arrangement. Besides it should be pointed outthat the need for such springs makes the embodiment complicated andnecessitates also as a rule, at least in more simple embodiments, needfor an increased length of the working arrangement. Finally, the work inconnection with mounting and replacement of such springs is risky sincethe springs must be applied with some pretensioning.

Another disadvantage with the prior art is that the costs for thedriving devices tend to be relatively high. In WO 92/11980 it isintended to use an internal combustion engine combined with a hydraulicpump of the kind normally appearing in hydraulic drive applications. Inthe European patent publication 0 051 853 it is suggested to use a partof a portable power saw and to combine this power saw part with ahydraulic pump. Such power saws are normally rather costly and will inthis intended application require a specially manufactured hydraulicpump or at least a specially manufactured coupling part. Usage of thepower saw part for its regular purpose requires dismounting of thehydraulic pump and application of power saw sword, chain etc.

SUMMARY OF THE INVENTION

The present invention aims at reducing the disadvantages discussedhereinabove.

According to a first aspect of the concept of the invention it isintended to provide ways to design the means for returning the workingchamber to a starting position without one having to rely on springs orsimilar elements based upon power accumulation. This aspect of theinvention is fulfilled by that primarily shown in FIGS. 1-3, namely anejector arrangement adapted to achieve evacuation of the working chamberand thereby returning of the working member by creating a negativepressure in the working chamber.

According to a second aspect of the invention it is aimed at providingways to reduce, to a minimum, the cost of the hydraulic fluid source,the latter at the same time being adapted to easily be used foralternative purposes without requiring substantial dismounting ormounting work. Essential in this connection is, furthermore, that the:hydraulic fluid source aimed at should be relatively widely spread andbe possible to purchase at a reasonable price.

This second aspect of the invention is fulfilled by the hydraulic fluidsource being constituted by a high pressure washing unit known per se orof an arbitrary nature. In that way a relatively non expensive unit isused as the hydraulic fluid source, said unit having a valuablealternative use after an easily executable decoupling of conduits bymeans of suitable quick couplings. Essential for this aspect of theinvention is, as is shown in the figures, that a fluid circulation isformed so that the fluid used, normally water, always circulates in thecirculation when the working member is passive. When the working memberis to be activated, the valve will, as a consequence of that shown inthe figures, divert the entire or a part of the flow of the circulationtowards the working chamber. In order to avoid detrimental overpressureconditions it is suitable to provide, as shown in the figures, apressure restriction valve. Other advantages and features of theconstruction according to the invention appear more closely by thefollowing description and the rest of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

With reference to the enclosed drawings a more specific description ofan embodiment example of the invention is presented hereunder.

In the drawings

FIG. 1 is a diagrammatical side view of the driving device according tothe invention applied on a fire wood cleaving machine;

FIG. 2 is a view similar to FIG. 1 but illustrating a state ofoperation; and

FIG. 3 is a partly cut and enlarged view illustrating parts of the firewood cleaving machine and the driving device according to the invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

The fire wood cleaving machine illustrated in the drawings comprises abase generally denoted 1 and being adapted to be supported relative tothe underlayer by means of suitable supports or legs 2.

The base 1 comprises at its upper part a support surface 3 for receivingwood pieces. This surface may for instance be cross sectionally V- orU-shaped in Order to form a seat for the wood pieces. At one end of thesupport surface there is arranged on the base 1 at least one edge member4. This edge member 4 protrudes upwardly above the support surface 3 andmay be arranged on a bracket like holder 5. At the other end of thesupport surface 3 a working arrangement 6 is provided. This has (seeFIG. 3) a working chamber 7 intended for receiving hydraulic fluid and aworking member 8 adapted to be put in motion on respective fluid supplyto and fluid evacuation from the working chamber 7. A basic part 9 ofthe working arrangement 6 is rigidly connected to the base 1. Theworking member 8 is adapted to move relative to this basic part 9. Theworking member 8 comprises, preferably, a particular contact member 10adapted to contact the wood piece.

In the example the working arrangement has the character of a hydrauliccylinder, the cylinder being formed by the basic part 9 and the pistonof the working member 8. The contact member 10 is arranged at theextreme end of the piston rod 11 of the piston 8.

When the piston 8 is caused to move relative to the cylinder 9, thecontact member 10 will hit a wood piece denoted 12 in FIG. 2 and forcethe same to move relative to the fixed edge member 4 so that a cleavagefunction occurs.

In case it would be desired to be able to use the device described forother pressing or power application purposes than fire wood cleaving perse, there may be on the base 1 fixing means 13, e.g. fixing holes, forsecuring particular dollies or other auxiliary equipment intended forspecific work purposes, said equipment being intended to function inco-operation with the power generating working arrangement 6.

The driving device according to the invention comprises a source 14 ofhydraulic fluid under pressure. Conduits collectively designated 15 areprovided for respective supply to and evacuation from the workingchamber 7 of hydraulic fluid. A valve 16 is adapted to, in a first state(FIG. 2), direct fluid to the working chamber 7 and, in a second state(FIGS. 1 and 3), allow evacuation of fluid from the working chamber.Means 17 are provided for returning the working member 8 to a startingposition (FIGS. 1 and 3).

The returning means 17 comprises an ejector arrangement adapted togenerate a negative pressure in the working chamber 7 for evacuating thesame as a consequence of flow of fluid through the ejector arrangement.

The hydraulic fluid source 14 comprises a pump 18 and a motor 19 drivingthe same, suitably an electric motor even if also other types of motors,e.g. internal combustion engines, may be in question.

The pump 18 of the hydraulic fluid source 14, the conduits 15, morespecifically parts of these conduits, and the valve 16, when it is inits second state; (FIGS. 1 and 3), define a fluid circulation, in whichthe ejector arrangement 17 is provided, there being a connection 20between the ejector arrangement 17 and the working chamber 7. In theexample this connection 20 has the character of a conduit of a certainlength but it should be noted that the connection 20 in practice couldbe extremely short, namely in case the ejector arrangement 17 would beprovided close to or integrated with the working arrangement 6.

The ejector arrangement 17 comprises at least one nozzle 21 arranged to,when the valve 16 is in its second state (FIGS. 1 and 3), cause thefluid to flow in such a way relative to an adjacent portion 22 of theconnection that a negative pressure occurs in the connection. Theejector arrangement 17 is in the example provided in a piece 23. Thenozzle 21 extends substantially axially relative to a passage 24 in thepiece 23, whereas the adjacent portion 22 of the connection 20 opensinto the passage 24 through its side, i.e. the mouth of the portion 22is directed at an angle, suitably a substantially right angle, to thedirection of the nozzle 21.

The valve 16 is in the embodiment provided downstream the ejector nozzle21 in the circulation. Resilient means 25 in the form of one or moresprings are provided to actuate the valve 16 to a normal position, whichis formed by the second state (FIG. 3).

In the embodiment it is illustrated that the valve 16 comprises amovable valve body 26, which in the first state entirely or partiallycloses or contracts the flow of fluid in the circulation and therebyforces fluid to flow to the working chamber 7 via the nozzle 21, thepassage 24, the mouth portion 22 and the connection 20. This state ofthe valve is indicated in FIG. 2. In the second state (FIG. 3) the valvebody 26 opens the circulation practically entirely, the fluid flowingthrough the ejector nozzle 21 applying, via the connection 20, anegative pressure in the working chamber 7, which involves evacuationthereof.

In the example the valve body 26 is rotatably movable and provided witha through opening, which by rotation of the valve body is caused toallow flow of fluid through the opening or close against flowtherethrough.

In the example it is illustrated that the valve body 26 is arranged inthe same piece 23 which also comprises the ejector arrangement 17. Thus,rotation of the valve body 26 gives rise to closing and openingrespectively of the passage 24 through the piece 23.

It is preferred that the valve body 26 is co-ordinated with a handle 27or other suitable operating member, the purpose of which is to primarilymanually operate the valve body 26. The actuation means 25 has, in theexample, the character of a spring acting between the operating member27 and a bracket 28 on the base 1. The purpose: therewith is that thevalve body 26 automatically should return to its second state (FIG. 3)when the operating member 27 is released.

Thus, the circulation described comprises the pump 18, the passage 24and the ejector nozzle 21 provided therein and the valve body 26 and aconduit section 29 between the pump 18 and the ejector arrangement 17and a second conduit section 30 extending between the valve 16 and pump18.

Besides, a hydraulic fluid tank 31 is arranged in the circulation. Theworking arrangement 6 is secured to the base 1 and a hollow part of thisbase forms the tank 31. In the example the conduit section 30 isconnected to the tank 31 with its end turned away from the pump 18,whereas the valve 16 via a conduit section 32 communicates with theinterior of the tank 31. The conduit section 32 is conceived to have arigid design and extends into the tank 31 so as to act as a turbulencedamper therein.

The conduit section 30 from the tank 31 is connected to the suction sideof the pump 18. The pressure side of the pump delivers at 33 highpressure fluid to the conduit section 29. In a connection 34 between thepressure side and suction side of the pump there is provided a valve 35opening on exceeding of a certain pressure on the pressure side. Thisopening point is suitably adjustable by means of an operating member 36.The valve 35 is formed by a conventional non-return valve. The purposeof the valve 35 is to ensure flow of fluid through the pump 18 also whenthe valve 16 is closed and the working chamber 7 at a maximum. Theconnection 34 could of course also extend between the conduit section 29and the interior of the tank 31 so that the pump would deliver, withopen valve 35, pressure fluid via the connection 34 into the tank 31,from which fluid would be sucked into the pump on its suction side.

The hydraulic fluid source 14 is formed by a high pressure washing unitknown per se or of an arbitrary nature. Such units are accessible on themarket at reasonable price and have surprisingly turned out to beoperable extremely well as a power source for the driving deviceaccording to the invention as a consequence of the design thereof suchthat a circulation of fluid through the pump 18 of the high pressurewashing unit is maintained under all normal conditions. It should bepointed out here that the fluid volume of the tank 31 should be at leastas large as the maximum volume of the working chamber 7 so that there isalways liquid in the tank 31 when the working chamber 7 is expanded to amaximum degree.

The high pressure washing unit 14 is very easily connectable to theconduit sections 29, 30 with conventional quick couplings. When the highpressure washing unit shall no longer be used as a power source in thedriving device, it is easily decoupled from the conduit sections 29 and30 and instead the suction side of the pump 18 is coupled to the watersupply network and its pressure side to a suitable spray nozzle.

When using the driving device according to the invention, the valve 16is in the position according to FIG. 3 as long as the working member 8is inactive. The pump 18 then delivers fluid to the conduit section 29at its pressure side and fluid flows in the previously describedcirculation through the ejector device 17 and the valve 16 into the tank31 and then via the conduit section 30 to the suction side of the pump18. Since the valve 16 is open, there is no risk for overheating of thepump 18. When the working member 8 is to be displaced, the operatoroperates the valve 16 so that its valve body 26 entirely or partiallycloses the flow past the valve. This means that the fluid pressure viathe connection 20 is propagated to the working chamber 7 with associatedfluid flow into the same and the working member 8 is displaced while theworking chamber is expanded. During this expansion the pump 18 deliverspressure fluid through the conduit sections 29, 20 whereas the pump onits suction side obtains fluid from the tank 31. When the working member8 reaches its end position and the working chamber 7 is at its maximum,the fluid ceases to flow into the same. If the operator then does notrelease the valve 16 for opening, the fluid ceases to flow on thepressure side of the pump 18, which causes a pressure increase, whichupon reaching of a certain level causes the non-return valve 35 to openso that fluid from the high pressure side of the pump flows over to thesuction side, whereby flow via the pump is always ensured.

When the valve 16 is allowed to return to the position according to FIG.3 by the operator, a fluid flow again occurs in the circulationdescribed. Fluid will then via the ejector nozzle 21 pass the adjacentmouth 22 of the connection 20 so that a fluid evacuating negativepressure occurs in the connection and the working chamber 7. Thisnegative pressure causes the working member or piston 8 to return to itsstarting position while reducing the volume of the working chamber 7.Thus, the normal position of the device in its inactive state is suchthat the valve 16 is then open and the ejector arrangement 17 alwaysensures via the connection 20 a negative pressure tending to retain theworking member 8 in its starting position with the working chamber 7 atits minimum.

The invention described can of course be modified in several ways withinthe scope of the invention. As already pointed out, the driving deviceaccording to the invention does not necessarily have to be applied inthe form of a fire wood cleaving machine or similar but quite differentapplications may be in question. As far as the use of a high pressurewashing unit as a hydraulic fluid source is concerned, it is herepointed out that a portable unit is primarily intended. In relation tothe ejector arrangement 17 it is pointed out that the mouth of theportion 22 of the connection 20 could of course also be directedsubstantially in parallel to the discharge direction from the nozzle 21.What is important with the invention in this regard is that the nozzle21 and the portion 22 of the connection 20 should be so mutually relatedthat when fluid flows out through the nozzle 21 a negative pressure iscreated in the connection 20 and the working chamber 7, this of coursepresuming that the flow way downstream the nozzle is not blocked.

I claim:
 1. A driving device comprising a source (14) of hydraulic fluidunder pressure, a working arrangement (6) having a working chamber (7)intended for receiving hydraulic fluid and a working member (8) adaptedto be put into motion on respective fluid supply to and fluid evacuationfrom the working chamber, at least one conduit for respective supply toand evacuation from the working chamber of hydraulic fluid, a valve (16)adapted to, in a first state, direct fluid to the working chamber and,in a second state, allow evacuation of fluid from the working chamber,and means (17) for returning the working chamber to a starting position,characterized in that the returning means (17) comprises an ejectorarrangement adapted to generate a negative pressure in the workingchamber (7) for evacuating the same as a consequence of flow of fluidthrough the ejector arrangement and there are resilient means (25) foractuating the valve to a normal position, which is constituted by thesecond state.
 2. A driving device according to claim 1, characterized inthat the hydraulic fluid source (14), which comprises a pump (18), theat lease one conduit and the valve (16), when it is in its second state,defines a fluid circulation, in which the ejector arrangement (17) isprovided, there being a connection (20) between the ejector arrangementand the working chamber (7).
 3. A driving device according to claim 2,characterized in that the ejector arrangement (17) comprises at leastone nozzle (21) adapted to, when the valve is in its second state, causefluid to flow such relative to an adjacent portion (22) of theconnection (20) that a negative pressure occurs in the connection.
 4. Adriving device according to claim 3, characterized in that the valve(16) is provided downstream the ejector nozzle (21) in the circulation.5. A driving device according to claim 4, characterized in that theworking arrangement (6) forms a part of a machine for splitting woodpieces, the working member (8) comprising a contact member (10) adaptedto contact wood pieces and force the same to move relative to a fixededge member (4).
 6. A driving device according to claim 2, characterizedin that the valve (16) is adapted, in its first state, to close orreduce flow in the circulation and instead direct fluid under pressureto the working chamber (7).
 7. A driving device according to claim 2,characterized in that a hydraulic fluid tank (31) is arranged in thecirculation.
 8. A driving device according to claim 7, characterized inthat the working arrangement (6) is secured to a base (1) and that ahollow part of the base forms said tank (31).
 9. A driving deviceaccording to claim 2, characterized in that a valve (35) opening onexceeding of a certain pressure on the pressure side is arranged in theconnection (34) between the pressure side and suction side of the pump.10. A driving device according to claim 1, characterized in that thehydraulic fluid source (14) is constituted by a high pressure washingunit.
 11. A driving device comprising a source (14) of hydraulic fluidunder pressure, a working arrangement (6) having a working chamber (7)intended for reception of hydraulic fluid and a working member (8)adapted to be put into motion on respective fluid supply to and fluidevacuation from the working chamber, at least one conduit for respectivesupply to and evacuation from the working chamber of hydraulic fluid,and a valve (16) adapted to, in a first state, direct fluid to theworking chamber and, in a second state, allow evacuation of fluid fromthe working chamber, characterized in that the hydraulic fluid source(14) is constituted by a high pressure washing unit.
 12. A drivingdevice according to claim 11, characterized in that a pump (18) includedin the high pressure washing unit, the at lease one conduit and thevalve (16), when it is in its second state, defines a fluid circulation.13. A driving device according to claim 12, characterized in that thevalve (16) is adapted, in its first state, to close or reduce flow inthe circulation and instead direct fluid under pressure to the workingchamber (7).
 14. A driving device according to claim 12, characterizedin that a hydraulic fluid tank (31) is arranged in the circulation. 15.A driving device according to claim 14, characterized in that theworking arrangement (6) is secured to a base (1) and that a hollow partof the base forms said tank (31).
 16. A driving device according toclaim 12, characterized in that a valve (35) opening on exceeding of acertain pressure on the pressure side is arranged in the connection (34)between the pressure side and suction side of the pump.
 17. A drivingdevice according to claim 11, characterized in that the workingarrangement (6) forms a part of a machine for splitting wood pieces, theworking member (8) comprising a contact member (10) adapted to contactwood pieces and force the same to move relative to a fixed edge member(4).
 18. A driving device comprising a source (14) of hydraulic fluidunder pressure, a working arrangement (6) having a working chamber (7)intended for receiving hydraulic fluid and a working member (8) adaptedto be put into motion on respective fluid supply to and fluid evacuationfrom the working chamber, at least one conduit for respective supply toand evacuation from the working chamber of hydraulic fluid, a valve (16)adapted to, in a first state, direct fluid to the working chamber and,in a second state, allow evacuation of fluid from the working chamber,and means (17) for returning the working chamber to a starting position,characterized in that the returning means (17) comprises an ejectorarrangement adapted to generate a negative pressure in the workingchamber (7) for evacuating the same as a consequence of flow of fluidthrough the ejector arrangement, and the hydraulic fluid source (14) isconstituted by a high pressure washing unit.
 19. A driving deviceaccording to claim 18, characterized in that there are resilient means(25) for actuating the valve to a normal position, which is constitutedby the second state.
 20. A driving device comprising a source (14) ofhydraulic fluid under pressure, a working arrangement (6) having aworking chamber (7) intended for receiving hydraulic fluid and a workingmember (8) adapted to be put into motion on respective fluid supply toand fluid evacuation from the working chamber, at least one conduit forrespective supply to and evacuation from the working chamber ofhydraulic fluid, a valve (16) adapted to, in a first state, direct fluidto the working chamber and, in a second state, allow evacuation of fluidfrom the working chamber, and means (17) for returning the workingchamber to a starting position, characterized in that the returningmeans (17) comprises an ejector arrangement adapted to generate anegative pressure in the working chamber (7) for evacuating the same asa consequence of flow of fluid through the ejector arrangement and thatthe hydraulic fluid source (14), which comprises a pump (18), the atleast one conduit and the valve (16), when it is in its second state,defines a fluid circulation, in which the ejector arrangement (17) isprovided, there being a connection (20) between the ejector arrangementand the working chamber (7), wherein the ejector arrangement (17)comprises at least one nozzle (21) adapted to, when the valve is in itssecond state, cause fluid to flow such relative to an adjacent portion(22) of the connection (20) that a negative pressure occurs in theconnection.
 21. A driving device comprising a source (14) of hydraulicfluid under pressure, a working arrangement (6) having a working chamber(7) intended for receiving hydraulic fluid and a working member (8)adapted to be put into motion on respective fluid supply to and fluidevacuation from the working chamber, at least one conduit for respectivesupply to and evacuation from the working chamber of hydraulic fluid, avalve (16) adapted to, in a first state, direct fluid to the workingchamber and, in a second state, allow evacuation of fluid from theworking chamber, and means (17) for returning the working chamber to astarting position, characterized in that the returning means (17)comprises an ejector arrangement adapted to generate a negative pressurein the working chamber (7) for evacuating the same as a consequence offlow of fluid through the ejector arrangement, and that the hydraulicfluid source (14), which comprises a pump (18), the at least one conduitand the valve (16), when it is in is second state, defines a fluidcirculation, in which the ejector arrangement (17) is provided, therebeing a connection (20) between the ejector arrangement and the workingchamber (7), further comprising a valve (35) opening on exceeding ofcertain pressure on the pressure side is arranged in the connection (34)between the pressure side and suction side of the pump.